A conventional rocking bearing is disclosed in WO2006/002905A1, for example. The rocking bearing disclosed in the above document includes an arcuate rocking bearing outer ring having a track surface on its inner diameter surface, a plurality of rollers disposed along the track surface, and a retainer for retaining the plurality of rollers. In addition, throughout a circumferential region of the rocking bearing outer ring, a flange portion is formed so as to project radially inward from each widthwise end portion thereof, in order to regulate the widthwise movements of the rollers and the retainer.
The above rocking bearing is used in an air disc brake device of a large-sized commercial car, a track, or a bus. In addition, the rocking bearing used in the air disc brake device is lubricated with grease in general.
Here, a description will be made of a case where a rocking bearing outer ring is built in a housing, with reference to FIGS. 26 and 27. First, referring to FIG. 26, when the curvature radius of a rocking bearing outer ring 101 is smaller than that of a housing 102, a gap is formed between the rocking bearing outer ring 101 and the housing 102. This gap causes the rocking bearing to wobble at the time of rocking.
Meanwhile, referring to FIG. 27, when the curvature radius of a rocking bearing outer ring 103 is larger than that of a housing 104, the rocking bearing outer ring 103 has to be built in while force (referred to as the pre-compression hereinafter) is applied to reduce its curvature radius.
However, when the difference in curvature radius between the rocking bearing outer ring 103 and the housing 104 is increased, high pre-compression has to be applied to build in the rocking bearing outer ring 103 by the above method. Meanwhile, as the pre-compression becomes high, rotation torque is increased at the time of rocking, which causes the rocking bearing to generate abnormal heat, and as a result, the rocking bearing to decrease its life span.
In addition, the above-described rocking bearing outer ring regulates the widthwise movements of the rollers and the retainer. However, the rocking bearing outer ring in this case cannot regulate the widthwise movements of the rollers and the retainer, so that the rollers and the retainer could separate in the radial direction of the rocking bearing outer ring and shift their positions at the time of shipping and assembling. This causes the number of assembling steps to increase and defective products to outflow.
Furthermore, since both circumferential end portions of the rocking bearing are open, grease is pushed outside at the time of rocking, which causes the grease to run out in the bearing. As a result, abnormal heat and abnormal wear are generated, which reduces the life span of the rocking bearing.